Objective:

Although associations between ambient air pollution and acute cardiorespiratory outcomes have been observed in numerous studies, questions remain about the degree to which these findings are generalizable between locations and whether the observed health effects are due to the individual pollutants measured or to pollutants acting in combination with other pollutants. In Project 4, we are conducting a multi-city time-series study to clarify the impacts of air quality on acute cardiorespiratory morbidity in five U.S. cities (Atlanta, GA; Birmingham, AL; Dallas, TX; Pittsburgh, PA; and St. Louis, IL-MO) using novel mixture characterization metrics. Our overarching hypothesis is that factors related to air pollution mixtures, seasonality and climate, concentration-response functions, exposure measurement error, and population susceptibility and vulnerability can help explain apparent between-city heterogeneity in short-term associations between air quality measures and cardiorespiratory emergency department (ED) visits.

Progress Summary:

During the current reporting period, work on Project 4 has focused on remaining data acquisition activities as well as single- and multi-city epidemiologic analyses.

Database development. Database activities included acquisition of the remaining health outcome data for the study. Health outcome data for Atlanta, Birmingham, Dallas, and St. Louis are complete. In the past year, a subcontract with University of Pittsburgh collaborators was continued as planned. University of Pittsburgh collaborators have acquired and processed ED visit data from Pittsburgh-area hospitals; for sharing these data with Emory, data use agreements between Emory and relevant Pittsburgh-area hospitals were finalized. Data were transferred to Emory at the end of the current reporting period and will be incorporated into epidemiologic analyses moving forward.

Data analyses. A number of data analysis activities were conducted over the reporting period:

We continued efforts on application of spatially-refined modeled estimates of ambient concentrations in multi-city epidemiologic analyses, including satellite-derived air quality estimates and the SCAPE data fusion approach, which combines monitoring and CMAQ modeled air quality data (Friberg, et al., submitted to ES&T), in health effect analyses and compared results with use of traditional monitoring-based exposure assignment approaches (Chang, et al., APHA, 2014; Sarnat, et al., ENV-VISION, 2015; Sarnat, et al., ISEE, 2015). Application of the different exposure metrics had a large impact on observed associations for NO2 and SO2, with stronger associations with use of data fusion exposure assignment approach, while associations for O3 and PM2.5 were largely similar across exposure assignment approaches. Results of these analyses also point to some consistency in estimated effects across four cities, such as strong positive associations of NO2 and PM2.5 with respiratory disease ED visits in all cities with no significant heterogeneity detected. Some heterogeneity in estimated effects across cities is also observed, such as strong positive associations for SO2 and respiratory ED visits in Birmingham and Dallas, but not in Atlanta or St. Louis; these findings are being further evaluated in multi-city effect modification analyses.

With the Air Quality and Biostatistics Cores, we continued work on methods for detecting and analyzing air pollution mixtures using multi-pollutant monitoring data: a) an approach for using classification and regression trees (C&RT) in multi-city air pollution epidemiologic research was published (Gass, et al., 2015); b) our self-organizing maps approach to characterizing air pollution mixtures was published (Pearce, et al., 2014) and an extension of this approach for use in epidemiologic analyses was also published (Pearce, et al., 2015) and will be presented at ISEE (Pearce, et al., ISEE, 2015); c) our approach to estimating the joint effects of multiple pollutants previously published (Winquist, et al., 2014) is being incorporated along with other approaches to estimating the effects of pollutant groups (Ye, et al., ISEE, 2015); d) working with Project 1, we have continued our examination of the effect of reactive oxygen species (ROS) on cardiorespiratory ED visits by retrospectively predicting DTT activity using a prediction model developed based on Project 1 data; results suggest a strong association between DTT and ED visits that is independent of the effect of PM2.5 (Bates, et al., submitted to ES&T; Bates, et al., CMAS 2015 abstract pending, Bates, et al., AAAR, 2015); and finally e) we used source apportionment to estimate daily mass concentrations of PM2.5 by source type for four US cities, and for sources similar in chemical composition between cities, we estimated associations with respiratory disease ED visits (Krall, et al., submitted to EHP; Krall, et al. JSM, 2015). We found PM2.5 from mobile sources, biomass burning, and dust was similar in chemical composition between cities, but PM2.5 from coal combustion and metal sources varied across cities. We found evidence of positive associations of ED visits for respiratory disease with PM2.5 from biomass burning and little evidence of associations with PM2.5 from dust. Associations with PM2.5 from mobile sources were not consistent across cities.

We continued work on examining detailed PM2.5 components data in epidemiologic analyses: a) analyses examining the health effects of a range of PM components from the St. Louis Supersite was published (Sarnat, et al., 2015); b) we applied and compared several approaches to estimating the effect of volatile organic compound chemical structure groups on cardiorespiratory ED visits in Atlanta (Ye, et al., ISEE, 2015); and c) we collaborated with the Biostatistics Core on a review article concerning statistical methods and challenges for estimating between PM components and health (Krall, et al., submitted to CEHR).

Finally, we assessed potential modifiers of the effects of ambient air pollution on health: a) multi-city analyses examining modification of air pollution-health associations by age were conducted and published for asthma (Alhanti, et al., accepted at JESEE) as well as for cardiovascular outcomes; b) analyses examining modification of air pollution-health associations by neighborhood socioeconomic factors were conducted for pediatric asthma/wheeze (O’Lenick, et al., submitted to JECH; O’Lenick, et al., SER 2015) as well as for cardiovascular outcomes; c) we continued work on estimating air exchange rates in each of the five cities and application of these data in epidemiologic models.

Future Activities:

Over the coming year, we anticipate completing our ED visit database by incorporating data from University of Pittsburgh collaborators. Manuscript preparation will begin and/or continue for analyses conducted over the past year. Current manuscripts in preparation include: 1) Exposure assignment considerations in a multi-city time-series study of ambient air pollution and cardiorespiratory emergency department visits; 2) Estimating the health effects of ambient volatile organic compounds; and 3) Relationship between warm-season ambient maximum temperature and emergency department visits across age groups. Additional planned manuscripts will focus on our multi-city assessment of air pollution and cardiovascular ED visits, further examination of retrospectively-predicted ROS on health, assessment of concentration-response function shape, assessment of air exchange rates as a modifier of ambient air pollution health effects, and extension of analyses considering modification of air pollution-health associations by neighborhood socioeconomic status to multiple cities.

Main Center Abstract and Reports:

Subprojects under this Center:(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).R834799C001 Development and Deployment of an Instrumentation Suite for Comprehensive Air Quality Characterization Including Aerosol ROSR834799C002 Examining In-Vehicle Pollution and Oxidative Stress in a Cohort of Daily CommutersR834799C003 Novel Estimates of Pollutant Mixtures and Pediatric Health in Two Birth CohortsR834799C004 A Multi-City Time-Series Study of Pollutant Mixtures and Acute Morbidity

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.